Sheet material accumulator

ABSTRACT

A veneer sheet stacking apparatus is described for moving sheets to a stacking station above a receiving platform and then discharging the sheets downward toward the receiving station. An accumulator is positioned on the apparatus for intercepting the descent of the discharged sheets and holding the sheets above the receiving platform until a desired number of sheets are accumulated to form a bundle. Then the entire bundle is released to drop the bundle onto the receiving station.

United States Patent Hayes [451 Mar. 28, 1972 [54] SHEET MATERIAL ACCUMULATOR [72] Inventor: Leonard L. Hayes, Lewiston, ldaho Potlatch Forests, Inc., San Francisco, Calif.

[22] Filed: Mar. 16,1970

[21] Appl.No.: 19,608

[73] Assignee:

[52] US. Cl ..214/6 DK, 271/68 [51] ..B65g 57/06 [58] Field of Search ..271/68; 214/6 DK, 6 H, 6 P,

[56] References Cited UNITED STATES PATENTS 2,759,615 '8/1956 Banks.

3,430,784 3/1969 Hall ...214/6 DK 2,767,534 10/1956 Nydegger et al. ...271/68 X 3,122,242 2/1964 Lopez et a1 ..214/6 DK 3,205,794 9/1965 Califano et a1. .214/6 DK X 3,410,421 11/1968 Groll ..214/6 DK 2,472,225 6/1949 Muddiman .214/6 DK X 2,622,876 12/1952 Schefe ..214/6 DK X Primary Examiner-Albert J. Makay Assistant ExaminerRobert J. Spar Attorney-Wells, St. John & Roberts [5 7] ABSTRACT A veneer sheet stacking apparatus is described for moving sheets to a stacking station above a receiving platform and then discharging the sheets downward toward the receiving station. An accumulator is positioned on the apparatus for intercepting the descent of the discharged sheets and holding the sheets above the receiving platform until a desired number of sheets are accumulated to form a bundle. Then the entire bundle is released to drop the bundle onto the receiving station.

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SHEET MATERIAL ACCUMULATOR BACKGROUND OF THE INVENTION This invention relates to equipment for stacking sheet material and more particularly to apparatus for stacking wood veneer sheets.

One of the principal problems that has perplexed the plywood industry for many years has been the problem of efficiently machine-handling and stacking the veneer sheets, particularly the green veneer sheets without damaging or breaking the sheets. Veneer sheets are quite brittle parallel to the grain and quite flexible and resilient perpendicular to the grain. The veneer sheets generally are of substantial size and occasionally have random defects. These physical characteristics of veneer sheets compound the difficulty of handling the sheets with automatic equipment. Furthermore it is found that if during the stacking process, a veneer sheet is dropped onto a stack the sheets will act similarly to sheets of paper and drift to one side or the other without landing squarely upon the stack. This makes it difficult to form a uniform stack with the sheets aligned with each other without either adjusting the top sheet when it reaches the stack or providing guides for containing the lateral movement of the sheet as it descends.

Another problem generally associated with automatic veneer sheet stackers is the requirement that the operation of the stacker be stopped momentarily while a complete stack is removed from the stacker. Such a stoppage seriously limits the capacity ofsuch machines.

One of the principal objects of this machine is to provide a new and novel accumulator for building up a desired number of sheets at the stacking station and then dropping the sheets in a bundle so that the sheets will fall vertically onto a receiving platform.

An additional object of this invention is to provide an accumulator that has a storage capacity sufficient to enable a finished stack to be removed from the stacking equipment without interrupting the stacking operation or the feeding equipment upstream of the stacker.

A further object of this invention is to provide an accumulator for a plywood stacker that is inexpensive to construct, reliable in operation and easy to maintain.

These and other objects and advantages of this invention will become apparent upon reading of the following detailed description ofa preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of this invention is illustrated in the accompanying drawings in which:

FIG. 1 is a fragmentary plan view of a sheet stacking apparatus for stacking veneer sheets at two stacking stations;

FIG. 2 is a fragmentary side view of the sheet stacking apparatus illustrated in FIG. 1;

FIG. 3 is a fragmentary longitudinal view taken along line 33 in FIG. 1 showing an ejector mechanism;

FIG. 4 is a vertical cross-sectional view taken along line 4- 4 in FIG. 1 illustrating an accumulator for supporting a desired number of sheets below the ejector mechanism and above a receiving station;

FIG. 5 is a fragmentary enlarged view of an operating mechanism of the accumulator; and

FIG. 6 is a fragmentary enlarged view similar to FIG. 5 except showing the accumulator releasing a number of sheets and dropping the sheets in unison.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT A stacking apparatus 10 is illustrated in the drawings for feeding and stacking plywood veneer sheets at stacking stations 11 and 12. Two stacking stations 11 and 12 are shown for illustration purposes, whereas additional stacking stations could be readily used as desired. The sheet stacking apparatus includes a feeding and discharge means 13 that is mounted on a base frame 14.

The feeding and discharge means 13 includes a substantially horizontal conveyor 16 for moving the wood sheets perpendicular to their grain from an upstream location in a substantially horizontal arched condition to the stacking stations. The conveyor 16 includes two endless opposing parallel belts 17 and 18 that are mounted at an inclined upright position for engaging the ends of the veneer sheets. The belts are spaced a distance less than the length of the sheets so that the sheets are transferred in an arched condition as shown in FIG. 4. The arching of the veneer sheets provides the sheets with a certain degree of rigidity. The conveyor 16 has a backing frame 20 for supporting the inner flights of the belt in an upward inclined manner. The endless belts l7 and 18 are mounted between conveyor end rollers 21.

Guide bars 23 and 24 are mounted along the belts on the inside for guiding the sheets horizontally along the conveyor and preventing the ends of the sheets from moving upward on the belts.

Discharge means 25 are located longitudinally along the conveyor at each of the stacking stations 11 and 12 for discharging the desired veneer sheets downwardly from the conveyor. The discharge means 25 includes opposing ejectors 26 and 27 that are positioned alongside the belts l7 and 18 respectively for engaging theends of the plywood sheets and forcing the ends downward from the belt, enabling the sheets to flatten out and descend downward in a path toward a receiving platform 33.

The ejectors 26 and 27 are operated by actuators 31 (FIG. 3) through linkages 33. When a veneer sheet arrives at the desired stacking station, the corresponding ejectors 26 and 27 operate to move the ends of the sheet downward from the belts towards the receiving platform 33.

At each stacking station is located a receiving platform 33 (FIG. 4) for receiving the sheets that are dropped by the discharge means. The receiving platform is mounted on a scissor lift 34. The lift 34 is weight sensitive and moves down incrementally as sheets are placed on the receiving platform. The scissor lift 34 is mounted on a wheel frame 35 so that a receiving platform having a full stack can be readily removed from the stacking station and an empty receiving platform moved into position for receiving sheets.

A principal aspect of this invention concerns an accumulator 38 mounted on the frame between the discharge means 25 and the receiving platform for receiving a desired number of sheets discharged from the discharge means and supporting said sheets to form a bundle and then dropping the supported sheets onto the receiving station in unison. It has been found that a bundle of veneer sheets descends substantially vertically with very little lateral movement.

The accumulator 38 includes two opposing support assemblies 40 and 41 (FIG. 4) that are mounted on opposite sides of the frame for extending into the path of ejected sheet veneers and engaging and holding the sheets adjacent the edges that are transverse to the wood grain until a desired number of sheets are gathered to form a bundle and then releasing the sheets to permit the entire bundle to descend to the receiving platform.

Each of the opposing support assemblies 40 and 41 (FIG. 5) has a skirt member 42 that normally extends downward at a slight outward incline angle which is sufficient to enable the arched sheet to flatten out as it descends. Each of the skirt members are pivotally mounted to the frame for pivotal movement about fixed parallel horizontal axes 43. Each of the skirt members 42 has a face surface 44 that provides a deflecting surface for guiding a discharged sheet downward. The skirt member has a lower end 45 with a hinge 46 mounted thereto. Support elements 47 are pivotally mounted to the lower ends for pivotal movement about movable axes 48.

The support element 47 is in the fonn of a plate having a face surface 51 that engages or receives the sheets that are ejected from the discharge means. Each of the support elements 47 has a back surface 52 with a horizontal hinge 53 mounted thereto. Each of the support elements 47 normally projects inward towards the other to extend into the path of the descending veneer sheets to support the sheets and prevent the sheetfrom descending to the receiving platform. After a desired number of sheets are accumulated, the support element is pivoted downward and outward from underneath the bundle of sheets as shown in FIG. 5 to release the bundle and permit the bundle to drop onto the receiving platform.

The accumulator 38 further includes a horizontal bracket 55 that isaffixed to the frame for slidably supporting a slide element 56. The slide element 56 has an elongated aperture 57 formed therein for receiving a stud shaft 58 to limit the longitudinal movement of the slide element on the horizontal bracket 55. A pivot member 60 is pivotally mounted on the slide element 56 for pivotal movement about a movable pivot axis at pivot point 61. The pivot member 60 has an upper end 62 that is affixed to the hinge 53 so that the support element 47 can pivot with respect to the upper end 62 of the pivot member 60.

The pivot element 60 has a deflecting surface 64 along the face thereof. Fluid actuators 66 are mounted on the frame and connected to the pivot members 60 through pivot rods 67 for pivoting the pivot members 60 about the pivot point 61 to swing the support elements 47 from beneath a bundle of onto the receiving platform 33. The compound action of the pivot members 60 and the support elements 47 about respective pivot points cause an extremely quick release to prevent the support elements 47 from interfering with the descent of the bundle. Furthermore, the operation of the actuator 66 pivots the support element 47 and the skirt member 42 about the fixed horizontal axis 43 and moves the pivot axis 48 outward to assist in the release.

In operation, the conveyor moves the veneer sheets to the stacking stations in arched positions. When the sheets arrive at the desired station the discharge means 25 ejects the sheets downward toward the receiving platform. The accumulator intercepts the sheets until a bundle is formed. Then the bundle of sheets is dropped onto the receiving station. When a stack is formed, the receiving platform is removed, with the accumulator holding the subsequently fed and discharged sheets until an empty platform is in position. In this manner there is no need to stop the feeding and discharge operations.

Numerous other embodiments may be readily devised by those skilled in the art while containing the principals of this sheets to release the bundle and to permit the bundle to fall invention. Therefore, only the following claims are intended to limit and define this invention.

What is claimed is:

1. An apparatus for stacking wood sheets at a stacking station comprising:

a receiving platform at the stacking station for receiving the wood sheets to form a stack, the wood sheets being rectangular veneer sheets having opposite edges transverse to the grain of the wood;

a feeding and discharge means mounted on a frame for sequentially feeding wood sheets to the stacking station vertically above the receiving platform and dropping the wood sheets one at a time toward the receiving station;

accumulator means mounted on the frame at the stacking station for gathering a desired number of the dropped sheets above the receiving platform to form a bundle and then releasing the bundle to drop the bundle onto the receiving platform in the formation of a stack;

said accumulator means comprising:

opposing support elements movably mounted on the frame for moving into and out of the path of the dropped sheets to selectively support the veneer sheets adjacent said opposite edges thereof; and

actuator means operatively connected to the support elements and responsive to the gathering of the desired number of sheets for moving the support elements into the path of the dropped sheets to support the sheets above the receiving platform until a bundle is formed and then moving the support elements out of the path of the dropped sheets to release the formed bundle of sheets and drop the bundle of sheets onto the receiving platform; opposing skirt members mounted to the frame for opposing 

1. An apparatus for stacking wood sheets at a stacking station comprising: a receiving platform at the stacking station for receiving the wood sheets to form a stack, the wood sheets being rectangular veneer sheets having oppoSite edges transverse to the grain of the wood; a feeding and discharge means mounted on a frame for sequentially feeding wood sheets to the stacking station vertically above the receiving platform and dropping the wood sheets one at a time toward the receiving station; accumulator means mounted on the frame at the stacking station for gathering a desired number of the dropped sheets above the receiving platform to form a bundle and then releasing the bundle to drop the bundle onto the receiving platform in the formation of a stack; said accumulator means comprising: opposing support elements movably mounted on the frame for moving into and out of the path of the dropped sheets to selectively support the veneer sheets adjacent said opposite edges thereof; and actuator means operatively connected to the support elements and responsive to the gathering of the desired number of sheets for moving the support elements into the path of the dropped sheets to support the sheets above the receiving platform until a bundle is formed and then moving the support elements out of the path of the dropped sheets to release the formed bundle of sheets and drop the bundle of sheets onto the receiving platform; opposing skirt members mounted to the frame for opposing pivoted movement about parallel fixed horizontal axes from a normal position in which the skirt members extend downward guiding the sheets downward from the feeding and discharge means and opposing support elements; and wherein the opposing support elements are pivotally connected to the skirt elements for movement about parallel movable horizontal axes so that when the actuator moves the support elements out of the path of sheets, the skirt members pivot outward to permit the bundle to drop freely. 